Technical Field
The present invention relates to a nanofluid containing a carbon nanotube and metal oxide nanoparticle composite and its use for increasing the heat transfer and specific heat capacity of a base fluid. More specifically, the present invention relates to a nanofluid containing a nanocomposite of multi wall carbon nanotubes and iron oxide, aluminum oxide, or copper oxide nanoparticles for increasing the heat transfer and specific heat capacity of water.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Many industrial and consumer products require the process of heat transfer for continuous operation. Convective heat transfer can be enhanced by changing flow geometry, boundary conditions, or by enhancing the thermal properties of the heat transfer fluid. The heat transfer of fluid is parameters which critically affects the cost and size of heat transfer systems. Conventional fluids like water and oils have limited heat transfer potential. Therefore, technologies that can improve a fluids thermal properties are of great importance. Improved heat transfer fluids would enable better engines in the automotive industry, more efficient machines in the heating, ventilation and air conditioning (HVAC) industry, higher efficiency flux devices in supercomputers, and provide new cancer treatment techniques.
The need for new classes of fluids with enhanced heat transfer capabilities is recognized by many different research groups around the world [J. C. Maxwell, Electricity and Magnetism, third ed., Clarendon, Oxford, 1904; C. W. Sohn, M. M. Chen, “Microconvective thermal conductivity in disperse two phase mixture as observed in a low velocity Couvette flow experiment” J. Heat Transfer, Trans. ASME 103 (1981) 47-51—each incorporated herein by reference in its entirety]. The advances in nanotechnology have made it possible to manufacture metal and metal oxide particles on a nano-dimensional scale. Nanoparticles are new generation materials with potential applications in the heat transfer area [Choi S. U. S. “Nanofluids: a new fluid of scientific research and innovative applications” Heat Transf. Eng. 2008, 29:429—incorporated herein by reference in its entirety]. In 1995 Choi was the first researcher who worked on the application of nanoparticles in fluid heat transfer at the Argonne National Laboratory, USA [Choi, S. U. S. “Enhancing thermal conductivity of fluids with nanoparticles” American Society of Mechanical Engineers, Fluids Engineering Division, Energy Systems Division, Argonne National Laboratory, 231:99-105, 1995—incorporated herein by reference in its entirety]. Choi defined these fluids as “an innovative new class of heat transfer fluids that can be engineered by suspending nanoparticles in conventional heat transfer fluids” and can lead to order-of-magnitude improvements in the thermal conductivity and convective heat transfer properties of traditional base fluids (ethylene glycol, water, oils) [Wenhua, Y., France, D., Choi, S. U. S., Routbort, J. L., “Review and Assessment of Nanofluid Technology for Transportation and Other Applications” Energy Systems Division, Argonne National Laboratory, April 2007—incorporated herein by reference in its entirety]. These heat transfer fluids with suspended ultrafine nanoparticles are dubbed “nanofluids.”
Nanofluids are typically engineered by suspending nanoparticles, preferably those possessing higher thermal conductivity, such as carbon, metal and metal oxides, with average sizes below 100 nanometers (nm) in traditional heat transfer fluids, such as water, oil, and ethylene glycol. Dispersants are also commonly added to avoid agglomeration of particles in the fluid, leading to homogeneous mixtures [P. Keblinski, 1. A. Eastman, and D. G. Cahill, “Nanofluids for thermal transport” Materials Today, 2005. 8(6): pp. 36-44; M. Bai, Z. Xu, and J. Lv, “Application of Nanofluids in Engine Cooling System” SAE International, 2008 Jan. 18, 2008; Zhou, D. W. “Heat transfer enhancement of copper nanofluid with acoustic cavitation” Int. J. Heat Mass Transfer 2004, 47, 3109-3117; Ding, Y., Alias, G., Wen, D., Williams R. A. “Heat transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids)” Int. J. Heat Mass Transfer 2006, 49, 240-250—each incorporated herein by reference in its entirety].
Many research groups have focused on the study of nanofluids by incorporating carbon nanotubes (CNTs). Choi and Zhang enhanced the thermal conductivity of engine oil by 160% when only 1 vol. % of carbon nanotubes (CNTs) were added to the oil [S. Choi, Z. Zhang, W. Yu, F. Lockwood, and E. Grulke, “Anomalous thermal conductivity enhancement in nanotube suspensions,” Applied Physics Letters, vol. 79, pp. 2252-2254, 2001—incorporated herein by reference in its entirety]. Assael et al demonstrated that CNTs can enhance the thermal conductivity of water [C. F. C. M. J. Assael, I. N. Metaxa, W. A. Wakeham, “Thermal conductivity of suspensions of carbon nanotubes in water” International Journal of Thermophysics vol. 25, pp. 971-985, 2004—incorporated herein by reference in its entirety]. Furthermore, a 38% enhancement in the thermal conductivity of the nanofluid was achieved when 0.6 vol. % of CNTs was added to water as a based fluid with Sodium Dodecyl Sulfate (SDS) as a dispersing agent [M. Assael, I. Metaxa, J. Arvanitidis, D. Christofilos, and C. Lioutas, “Thermal conductivity enhancement in aqueous suspensions of carbon multi-walled and double-walled nanotubes in the presence of two different dispersants” International Journal of Thermophysics, vol. 26, pp. 647-664, 2005—incorporated herein by reference in its entirety].
In 2005 Liu et al., [M.-S. Liu, M. C.-C. Lin, I.-T. Huang, and C.-C. Wang “Enhancement of thermal conductivity with carbon nanotube for nanofluids,” International Communications in Heat and Mass Transfer, vol. 32, pp. 1202-1210, 2005—incorporated herein by reference in its entirety] investigated the thermal conductivities of water mixed with three different types of nanoparticles (CNTs, CuO, SiO2). They reported that a 11.3% improvement of the thermal conductivity was achieved when 0.01% volume of the nanoparticles were added. Ding et al., measured the heat transfer of water mixed with low concentrations of CNTs (0.5-1 vol. %) and an Arabic gum dispersant. Under such conditions, an enormous enhancement in the heat transfer of 350% at Re=800 was obtained [Ding, Y., Alias, H., Wen, D., Williams, R. A.; “Heat Transfer of aqueous suspensions of carbon nanotubes (CNT nanofluids)”, International Journal of Heat and Mass Transfer, vol. 49, pp. 240-250, 2006—incorporated herein by reference in its entirety]. In 2007, Koa et al. [Koa, G. H., Heo, K., Lee, K., Kim, D. S., Kim, C., Sohn, Y., Choi, M. “An experimental study on the pressure drop of Nanofluids containing carbon nanotubes in a horizontal tube,” International Journal of Heat and Mass Transfer, vol. 50, pp. 4749-4753, 2007—incorporated herein by reference in its entirety] measured the viscosity and the pressure drop characteristics of carbon nanotubes dispersed in water. They observed an increase in the viscosity of the solution due to the suspended solid nanoparticles (CNTs) and a reduction of the pressure drop. Wu et al. [Wu, X., Wu, H., Cheng, P. “Pressure drop and heat transfer of Al2O3—H2O nanofluids through silicon microchannels” Journal of Micromechanics and Microengineering, 19(10):105020 (11 pp.), 2009—incorporated herein by reference in its entirety] used alumina nanoparticles dispersed in water at two different concentrations (0.15 and 0.26 vol. %) and performed in laminar flow (Re varied from 190 up to 1020) to measure the heat of the nanofluid. In this experiment, a trapezoidal micro-tube made of silicon was used, heated by a constant DC power supply. The highest increment of the heat transfer was 15.8% for 0.26 vol. %. Using Al2O3 nanoparticles dispersed in water at laminar conditions using a rectangular microchannel connected with a DC power supply, Ho and his research group, [Ho, C. J., Wei, L. C., Li, Z. W., “An Experimental Investigation of Forced Convective Cooling Performance of a Microchannel Heat Sink with Al2O3/water nanofluid”, Applied Thermal Engineering, 30(2-3):96-103, 2010—incorporated herein by reference in its entirety] observed up to 30% (average value) increases in heat transfer coefficients at 1 vol. % of Al2O3 nanoparticles and a Reynolds number at 1544. Anoop, et al., [Anoop, K. B., Sundararajan, T., Das, S. K. “Effect of particle size on the convective heat transfer in nanofluid in the developing region” International Journal of Heat and Mass Transfer, 52(9-10) 2009, 2189-2195—incorporated herein by reference in its entirety] studied the effect of different alumina nanoparticles sizes on the heat transfer of water with a Reynolds number from 500 to 2000 and laminar flow. The results showed smaller nanoparticles led increased heat transfer (25%) and thermal conductivity (6%) at a Reynolds number of 1550. The larger nanoparticles raised the heat transfer by only 11%. Mohammed, et al. [Mohammed, H. A., Bhaskaran, G., Shuaib, N. H., Abu-Mulaweh, H. I. “Influence of nanofluids on parallel flow square microchannel heat xchanger performance” International Communications in Heat and Mass Transfer, 38(1) 2011, 1-9—incorporated herein by reference in its entirety] studied the effect of different types of nanoparticles such as silver, silicon dioxide, aluminum oxide and titanium dioxide nanoparticles in the heat transfer of water as nanofluids under laminar flow conditions. In this study, the effect of changing the Reynolds number from 100 to 800 and also the volume fraction of particles at 2%, 5% and 10% was also evaluated. This study demonstrated that silver had the lowest pressure drop and that alumina provided the highest heat transfer coefficient. A recent study conducted by MinSheng Liu et al. in 2011 [MS. Liu, M. C. C. Lin, C C. Wang “Enhancements of thermal conductivities with Cu, CuO, and carbon nanotube nanofluids and application of MWNT/water nanofluid on a water chiller system,” Nanoscale Research letters, vol. 6, 2011, p. 297—incorporated herein by reference in its entirety] investigated the enhancement of thermal conductivity of nanofluids prepared by using a two-step method for dispersing copper oxide (CuO) and carbon nanotubes in water, ethylene glycol and synthetic oil without using surfactants. Their results show that nanofluids with low volume concentrations of nanoparticles have the greatest thermal conductivity. A 4.2% increase in cooling capacity of nanofluids at a flow rate of 100 L/min was observed under these conditions. It was also shown that the heat performance coefficient of the water chiller increased by 5.15% relative to that without nanofluids. The researchers also concluded that the dynamic effect (dispersion) may effectively enhance system performance.
While many studies have been conducted on nanofluids containing carbon nanotubes and/or metal oxides, investigations regarding the thermo-physical properties of nanofluids containing impregnated CNTs with metal oxides are scarce.
In view of the forgoing, the objective of the present invention is to provide nanofluids containing carbon nanotubes and metal oxide nanoparticle composites with advantageous thermo-physical properties such as specific heat capacity, viscosity, heat transfer rate and pressure drop.